WO2012/104625 describes a scanning probe microscope comprising a probe that is mechanically responsive to a driving force. A signal generator provides a drive signal to an actuator that generates the driving force, the drive signal being such as to cause the actuator to move the probe repeatedly towards and away from a sample. An interferometer is arranged to output a height signal indicative of a change in path difference between light reflected from the probe and a height reference beam. Image processing apparatus is arranged to use the height signal to form an image of the sample.
Movement of the probe is accompanied by an angular deflection of the back surface of the cantilever which reflects the light into the interferometer. It has been assumed historically that this change of angle of the cantilever does not affect the height measured by the interferometer.
In a more conventional scanning probe microscope (unlike the microscope of WO2012/104625) the measurement of height change to the tip due to bending of the cantilever is not required, as a feedback system is used to maintain the cantilever at a constant deflection by adjusting the position of the base of the probe.